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From: Mike Galbraith <efault@gmx.de>
To: LKML <linux-kernel@vger.kernel.org>
Cc: Paul Menage <menage@google.com>, Colin Cross <ccross@android.com>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Ingo Molnar <mingo@elte.hu>, Li Zefan <lizf@cn.fujitsu.com>
Subject: query: [PATCH 2/2] cgroup: Remove call to synchronize_rcu in cgroup_attach_task
Date: Thu, 07 Apr 2011 11:55:53 +0200	[thread overview]
Message-ID: <1302170153.12304.31.camel@marge.simson.net> (raw)

Greetings,

Wrt these patches:

https://lkml.org/lkml/2010/11/24/14 [PATCH 1/2] cgroup: Set CGRP_RELEASABLE when adding to a cgroup
https://lkml.org/lkml/2010/11/24/15 [PATCH 2/2] cgroup: Remove call to synchronize_rcu in cgroup_attach_task

I received a query regarding 2/2 because a large database company is
apparently moving tasks between cgroups frequently enough that their
database initialization time dropped from ~11 hours to ~4 hours when
they applied this patch.

Curious why these got no traction.

Regardless of the wisdom of frequent cgroup moves, Joe User launching
light tasks via cgexec would gain quite a bit as well it seems.

Q/D measurement of cgexec -g cpu:test sh -c exit.

Unpatched:

marge:~ # time perf stat --repeat=1000 cgexec -g cpu:test sh -c exit

 Performance counter stats for 'cgexec -g cpu:test sh -c exit' (1000 runs):

          2.686149 task-clock-msecs         #      0.119 CPUs    ( +-   0.067% )
                 2 context-switches         #      0.001 M/sec   ( +-   0.100% )
                 0 CPU-migrations           #      0.000 M/sec   ( +-  35.231% )
               633 page-faults              #      0.236 M/sec   ( +-   0.003% )
           6292755 cycles                   #   2342.668 M/sec   ( +-   0.062% )
           4844702 instructions             #      0.770 IPC     ( +-   0.004% )
            974011 branches                 #    362.605 M/sec   ( +-   0.005% )
             35187 branch-misses            #      3.613 %       ( +-   0.027% )
     <not counted> cache-references        
     <not counted> cache-misses            

        0.022597372  seconds time elapsed   ( +-   0.981% )


real    0m23.054s
user    0m0.380s
sys     0m0.000s

Patched:

marge:~ # time perf stat --repeat=1000 cgexec -g cpu:test sh -c exit

 Performance counter stats for 'cgexec -g cpu:test sh -c exit' (1000 runs):

          2.639303 task-clock-msecs         #      0.915 CPUs    ( +-   0.051% )
                 1 context-switches         #      0.000 M/sec   ( +-   1.048% )
                 0 CPU-migrations           #      0.000 M/sec   ( +-  21.602% )
               633 page-faults              #      0.240 M/sec   ( +-   0.003% )
           3883572 cycles                   #   1471.439 M/sec   ( +-   1.767% )
           4830809 instructions             #      1.244 IPC     ( +-   0.191% )
            975204 branches                 #    369.493 M/sec   ( +-   0.009% )
             35314 branch-misses            #      3.621 %       ( +-   0.060% )
     <not counted> cache-references        
     <not counted> cache-misses            

        0.002884424  seconds time elapsed   ( +-   0.055% )


real    0m3.329s
user    0m0.012s
sys     0m0.352s




             reply	other threads:[~2011-04-07  9:56 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-04-07  9:55 Mike Galbraith [this message]
2011-04-13  2:02 ` query: [PATCH 2/2] cgroup: Remove call to synchronize_rcu in cgroup_attach_task Li Zefan
2011-04-13  3:11   ` Mike Galbraith
2011-04-13 13:16     ` Paul Menage
2011-04-13 16:56       ` Mike Galbraith
2011-04-14  7:26         ` Mike Galbraith
2011-04-14  8:34           ` Mike Galbraith
2011-04-14  8:44             ` Mike Galbraith
2011-04-18 14:21       ` Mike Galbraith
2011-04-28  9:38         ` Mike Galbraith
2011-04-29 12:34           ` Mike Galbraith
2011-05-02 13:46             ` Paul E. McKenney
2011-05-02 14:29               ` Mike Galbraith
2011-05-02 15:04                 ` Mike Galbraith
2011-05-02 23:03                   ` Paul E. McKenney
2011-04-13 13:10 ` Paul Menage
2011-04-13 16:52   ` Mike Galbraith

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